In the related art, there is a known laser source apparatus for laser microscope that generates laser beams having a plurality of wavelengths by splitting a laser beam having a single wavelength emitted from a single laser source into two beams and converting one wavelength of these laser beams with an optical parametric oscillator (OPO) (for example, see Patent Literature 1 and Patent Literature 2).
Compared with a laser source apparatus using a plurality of sources, this kind of laser source apparatus has superior timing control among the plurality of laser beams particularly when using pulsed laser with an extremely short pulse width, such as femtosecond-pulse laser or picosecond-pulse laser. Therefore, it is suitable for using ultrashort-pulse laser beams having a plurality of wavelengths for simultaneously observing a plurality of fluorescences from a multi-colored specimen or for simultaneously performing light stimulation and observation. In addition, laser beams having a plurality of wavelengths can be used with a low-cost configuration compared with an apparatus equipped with a plurality of laser sources.